IMO, many (most?) people quite simply don't think about things. They just have some dogmatic positions they've taken for some reasons, and they regurgitate them as necessary.
And that's a lot of the reason that they so often and so brazenly misinterpret things other people say. They're not actually reading to comprehend - they're reading just to get enough of a feel for it to classify it, so that they'll have some (potentially quite wrong) idea of which bit of rhetoric to trot out in response to it.